Aromatic dicarboxylic acid chlorides which are used for the preparation of aromatic oligomeric and polymeric bisphenol esters are prepared according to U.S. Pat. No. 4,129,594, the case of the simplest terephthalic acid bis-bisphenol A ester, for example, being included. The polyesters can be further converted into polyester-carbonates by reaction with COCl.sub.2. The particular bis-bisphenol A esters cannot be isolated in this preparation method, rather, a mixture of bisphenol esters with very diverse degrees of polymerization is in each case obtained, which has the result that the polyester-polycarbonates obtained from these mixtures with COCl.sub.2 do not have a controlled segment build-up.
Corresponding comments apply to DE-OS (German Published Specification) No. 3,026,937.
In another synthesis route for polyester-carbonates, finished polycarbonate is used as the starting material (see, for example, U.S. Pat. No. 3,998,908, British Patent Specification No. 954,500 and British Patent Specification No. 898,775). In this melt process, the polycarbonates can be partly degraded (U.S. Pat. No. 3,988,908) while they are reacted with the end groups of the polyesters. However, complete degradation of the polycarbonates with reaction of the COOH groups of the polyesters is neither intended here, nor should it take place de facto (see, for example, U.S. Pat. No. 3,998,908, column 4, lines 47-54 and column 2, lines 56-61 and column 6, lines 8-46).
In the preparation of branched polycarbonates, branching agents containing carboxylic acid are likewise incorporated (see British Patent Specification No. 1,159,924, U.S. Pat. Nos. 3,816,373 and 4,001,184). However, in this case also, no monomeric ester-triphenols or ester-tetraphenols and the like are obtained.
According to German Patent Specification No. 2,254,918 (LeA 14,711), ortho-esters containing phenolic OH groups are prepared and are used as branching agents for thermoplastic polycarbonates. The ortho-esters are prepared by transesterification of ortho-acrylates with diphenols, that is to say by a process different from that of the present invention.
Bisphenol A tetraphthalate-carbonate copolymers and their preparation from bisphenol A, tetraphthalyl chloride, phenols and phosgene are described according to DE-OS (German Published Specification) No. 2,714,544. However, in our opinion, the polyester-carbonates having the regular structure build-up according to the present invention are not achieved by the process of this literature reference.
According to European Patent Specification No. 2,218 (LeA 18,544), aromatic polyesters are prepared in the presence of aromatic polycarbonates by a transesterification process, also using bisphenols and diaryl esters of aromatic dicarboxylic acids. This process also does not give the polyester-carbonates of the present invention having the regular structure build-up.
De-OS (German Published Specification) No. 2,636,783 (LeA 16,689) and DE-OS (German Published Specification) No. 702,626 (LeA 17,356) describe the direct incorporation of carboxylic acids above a certain molecular weight together with diphenols and phosgene by the phase boundary process for the preparation of polyester-carbonates. Again, it cannot be expected that the polyester-carbonates of the present invention having the regular structure build-up are obtained.